Her pairs partner was Ben Barruco, with whom she placed 2nd at the novice level at the 1997 Canadian Championships. Championships is second only to Michelle Kwan (38).
She did not compete with either partner internationally. Belbin / Agosto won the silver medal at the 2005 World Championships.
She competed both as a pair skater and ice dancer in Canada before deciding to concentrate completely on ice dancing.
She was introduced to ice dancing by Paul Wirtz and competed with partner Liam Dougherty.
Instead, Belbin and Agosto were sent to all the other ISU Championships for which they were eligible: Four Continents, Junior Worlds, and Worlds. At Nationals in 2005, the last year of the 6.0 system, Belbin / Agosto received straight perfect sixes for presentation in their free dance. Bush signed on December 31, 2005, Belbin became a naturalized citizen, allowing her to compete for the United States at the 2006 Winter Olympics.
They won the 2002 World Junior Championships, completing their set of medals from that event. In January 2006, Belbin / Agosto won their third consecutive national title and qualified for the Olympics.
With Agosto, Belbin is the 2006 Olympic silver medalist, four-time World medalist, three-time Four Continents champion (2004–2006), and five-time U. Tanith Belbin began her naturalization process in 2000, but due to changes that were made to the law in 2002, the process has taken significantly longer than it would have if she had filed her paperwork two years later." Her father, Charles Belbin, is a public relations manager, while her mother, Michelle (Mc Kinlay) Belbin, is a former figure skater (who trained in St.